1. Field of the Invention
This invention relates to an orthopedic hook system for use in correcting scoliosis.
2. Description of the Prior Art
Scoliosis is a medical term that denotes an abnormal curvature of the spine. This abnormality usually occurs as a single primary curvature or as primary curvature accompanied by a compensating secondary curvature.
Where the spine is curved from side-to-side, the condition is known as nonstructural scoliosis. If the spine is not only curved but also twisted, the condition is known as structural scoliosis.
There are varying degrees of scoliosis ranging from where the condition is hardly visible to where the deviation of the natural curvature can have an adverse impact on a person""s lung capacity, personal appearance, and ability to engage in physical activities. This is in addition to the emotional and psychological impact a person may suffer due to the disfiguring nature of the condition.
One method of correcting this condition is to surgically install a series of rods and supporting devices to reconfigure the spine to approximate a more normal curvature. In this process, a number of supporting devices incorporate a hook that comes into contact with the bones of the spine.
U.S. Pat. Nos. 4,411,259 to Drummond (the ""259 patent), 5,863,293 to Richelsoph (the ""293 patent), 5,964,760 to Richelsoph (the ""760 patent), 6,083,226 to Fiz (the ""226 patent), 6,117,136 to Von Strempel (the ""136 patent), 6,132,432 to Richelsoph (the ""432 patent) and 6,179,838 to Fiz (the ""838 patent) all disclose a hook as part of a bone fixation device for use with a series of rods to secure the spine, or regions of the spine, in a particular position. In each case identified, the hook is placed into contact with an element of the bone such as the laminar part of the vertebra. The hook remains in place due to the forces created by the system of fixation devices, rods, and to some degree the force of the spine in opposition to the corrective measures.
Since the hooks in the aforementioned patents do not clamp against the bone to remain in place when initially installed, the hooks are movable when first put into place. This can cause problems when a hook slips, or moves, into a position that is not desirable while the remaining hooks and rods are being secured into place. Not only is it time consuming to correct the positioning of the hook, but due to the location of the instruments about the spinal column there is an increased risk of problems arising due to improper movement of the hook.
Another problem arises in securing the rod to the fixation device. Due to the side-to-side and potential twisting movement of the spine found in cases of scoliosis, the fixation devices may not be level in relation to one another at the beginning of the operative procedure. Thus the fixation device must have a rod engaging element that is long enough to capture the rod when the rod is at a greater distance from the fixation device.
The ""432, ""760, and ""293 patents all disclose a rod receiving mechanism that has two arms that are designed to encompass the rod and aid in directing the rod toward a seat thereby securing the rod in place. Naturally, these devices could be manufactured with very long arms to capture a rod at almost any practical distance from the fixation device. However, this creates another problem.
When the rod is finally secured into position, the portion of the arms that are not operating with the locking ring or set screw may be so long that it creates complications. This excess threaded metal surface is not desirable in the area of the spine. Furthermore, the distance between the bones of the spine and the surface of the skin on a patients back is not very great. The arms must be short enough to be completely covered by the patient""s flesh when the operation is complete.
What is needed is a hook that can be secured in place while performing the scoliosis correcting procedure and arms that are long enough to engage the rod and yet can be reduced in length when the rod is in place so that there is little if any excess threaded metal beyond the securing cap or screw.
The invention is directed to an orthopedic hook system comprising a hook shaped clamping section being substantially saddle shaped for receiving a bone segment and a rod receiving section, the clamping section has a threaded opening extending through the hook shaped clamping section and an upper side. A grip screw is adapted to work in cooperation with the threaded opening to secure the bone segment in place within the hook shaped clamping section. The rod receiving section is substantially U-shaped and has a threaded inside surface and a base adapted to receive the rod with the rod receiving section extending above the upper side of the hook shaped clamping section. A cap is adapted to fit over the substantially U-shaped rod receiving cavity and has a concave surface for engaging the rod, and a set screw adapted for use with the threaded inside surface of the substantially U-shaped rod receiving section such that the set screw engages the cap, which in turn secures the rod between the cap and the base of the rod receiving section.